Scanning apparatuses are widely used for scanning images of paper documents. The scanned images can be converted into electronic files, which are then stored, processed or spread. With the maturity of scanning technologies, the scanning apparatuses have experienced great growth and are now rapidly gaining in popularity.
FIG. 1 is a schematic perspective view illustrating a conventional scanning apparatus. As shown in FIG. 1, the conventional scanning apparatus 1 comprises a lower casing 10 and an upper cover 11. The lower casing 10 comprises a glass platform 101 and a scanning module 102. The glass platform 101 is used for scanning a to-be-scanned document P (see FIG. 2). After the document P is placed on the glass platform 101, the lower casing 10 is covered by the upper cover 11, so that the document P is positioned in the scanning apparatus 1. During the scanning operation is performed, the scanning module 102 is moved within the lower casing 10 to scan the document P.
Hereinafter, the internal structure of the lower casing 10 of the conventional scanning apparatus 1 will be illustrated with reference to FIG. 2. FIG. 2 is a schematic side view illustrating the conventional scanning apparatus. As shown in FIG. 2, in addition to the glass platform 101 and the scanning module 102, the lower casing 10 further comprises a transmission shaft 103 and a driving motor 104. The scanning module 102 is installed on the transmission shaft 103. The driving motor 104 is connected with the scanning module 102 for providing motive power to the scanning module 102, so that the scanning module 102 is moved along the transmission shaft 103. The scanning module 102 comprises a light guide module 105, a fixed reflective mirror 106, a lens 107 and an optical sensing element 108. The light guide module 105 is used for emitting light beams L and projecting the light beams L on the document P. The light guide module 105 is a lamp tube. The light beams L reflected by the document P are reflected by the fixed reflective mirror 106, and then focused by the lens 107. The focused light beams L are received by the optical sensing element 108, and then converted into corresponding image signals of the document P.
Hereinafter, a process for performing a scanning operation by the scanning apparatus 1 will be illustrated with reference to FIGS. 1 and 2. For scanning the document P by the scanning apparatus 1, the document P is firstly placed on the glass platform 101 of the lower casing 10. Then, the upper cover 11 is rotated toward the lower casing 10 to cover the lower casing 10 and fix the document P. After the document P is fixed, the scanning apparatus 1 is activated, and a scanning operation for scanning the document P starts. Meanwhile, the light guide module 105 of the scanning module 102 emits light beams L and projects the light beams L on the document P. The light beams L reflected by the document P are reflected by the fixed reflective mirror 106, and then focused by the lens 107. The focused light beams L are received by the optical sensing element 108, and thus a first portion of the image of the document P is acquired. Moreover, when the scanning apparatus 1 is activated, the driving motor 104 is enabled to drive movement of the scanning module 102 along the transmission shaft 103. That is, the overall document P is scanned while moving the scanning module 102 along the transmission shaft 103. After the scanning operation is finished, the complete image of the document P is acquired.
Hereinafter, the structure of the light guide module 105 will be illustrated with reference to FIG. 3. FIG. 3 is a schematic front view illustrating the light guide module of the conventional scanning apparatus. The light guide module 105 comprises a base 1051, a circuit board 1052, a front-emitting LED (light emitting diode) 1053, a light-guiding bar 1054 and a heat sink 1055. The circuit board 1052 is disposed at a first end of the base 1051. The light-guiding bar 1054 is disposed on the base 1051. The front-emitting LED 1053 is mounted on the circuit board 1052 for emitting light beams L from the first end of the base 1051 and projecting the light beams L to the light-guiding bar 1054. The light beams L are guided by the light-guiding bar 1054 to be projected on the document P. The heat sink 1055 is disposed at the first end of the base 1051 for removing the heat that is generated from the front-emitting LED 1053 upon illumination.
Since only a single front-emitting LED 1053 is included in the light guide module 105, the front-emitting LED 1053 of the light guide module 105 is usually a high power LED for providing sufficiently bright light beams to scan the document P. However, since the front-emitting LED 1053 is a high power LED, the area of the heat sink 1055 should be large enough to dissipate the heat. Under this circumstance, the scanning apparatus 1 should provide a large space for accommodating the heat sink 1055. In other words, the large-sized heat sink 1055 is detrimental to miniaturization of the scanning apparatus 1.
After the plural light beams L emitted by the light guide module 105 are projected on the document P, the light beams L reflected by the middle portion of the document P are sequentially reflected by the fixed reflective mirror 106, focused by the lens 107, and received by the optical sensing element 108. Similarly, the light beams L reflected by the both edges of the document P are also sequentially reflected by the fixed reflective mirror 106, focused by the lens 107, and received by the optical sensing element 108. Generally, the quantity of the light beams L reflected by the middle portion of the document P to be received by the optical sensing element 108 is higher than the quantity of the light beams L reflected by the edges of the document P to be received by the optical sensing element 108. During the process of scanning the document P, since the both edges of the documents P are relatively darker, the scanning quality is deteriorated. That is, since the light beams L emitted by the light guide module 105 are not uniformly distributed, the light beams L fail to be uniformly received by the optical sensing element 108. Under this circumstance, the scanning quality of the scanning module 102 is impaired.
Therefore, there is a need of providing a light guide module for enhancing the scanning quality and reducing the volume of the scanning apparatus.